1. Field of the Invention
The present invention relates to a sheet material feeding apparatus which takes a sheet material one by one from a sheaf of the plural stacked sheet materials and then transports the taken sheet materials, and more particularly, to a sheet material feeding apparatus which is provided with a mechanism for preventing so-called multifeeding (or overlap feeding) that plural sheet materials are fed together when a one-time feeding operation is performed.
2. Related Background Art
Conventionally, as an automatic sheet feeding apparatus which is provided with a multifeeding prevention mechanism of retard system, for example, there is provided a system in which an operation to urge a pressure plate for causing a stacked sheet to come into pressure-contact with a paper (or sheet) feeding roller into the paper feeding roller and to move (or shift) the pressure plate to release it from the paper feeding roller is driven by rotation of the shaft of the paper feeding roller with use of a cam on this shaft. In this system, when the pressure plate is urged to the side of the paper feeding roller, a contact speed between the sheet on the pressure plate and the paper feeding roller is restrained by driving the paper feeding roller at low speed, so as to reduce a crush sound made when the sheet comes into contact with the paper feeding roller.
Further, when a driving force from a motor is transmitted to the paper feeding roller, a planet gear clutch or the like might be used to transmit the driving force to other units in the middle of its transmission system. In this case, even if the motor is driven at low speed, the cam on the shaft of the paper feeding roller is pressed by a cam of the pressure plate, and a gear engaging portion of a planet gear is thus released, whereby an antecedent rotation phenomenon of the paper feeding roller occurs. Thus, the contact speed between the sheet and the paper feeding roller can not be restrained, whereby the crush sound can not be reduced resultingly.
As described above, in the conventional automatic sheet feeding apparatus, there are some restrictions in the case where the contact speed between the sheet on the pressure plate and the paper feeding roller is restrained and the crush sound made when the sheet comes into contact with the roller is thus restrained. That is, in the automatic sheet feeding apparatus which is provided with the pressure plate for causing the stacked sheet to come into contact with the paper feeding roller, since a driving source such as a motor or the like which is dedicated for the automatic sheet feeding apparatus is used, the apparatus becomes large in size and brings an increase in cost.